From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Mladek Date: Wed, 30 Mar 2016 15:53:27 +0000 Subject: [PATCH v4 2/5] printk/nmi: use IRQ work only when ready Message-Id: <1459353210-20260-3-git-send-email-pmladek@suse.com> List-Id: References: <1459353210-20260-1-git-send-email-pmladek@suse.com> In-Reply-To: <1459353210-20260-1-git-send-email-pmladek@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org NMIs could happen at any time. This patch makes sure that the safe printk() in NMI will schedule IRQ work only when the related structs are initialized. All pending messages are flushed when the IRQ work is being initialized. Signed-off-by: Petr Mladek Cc: Jan Kara Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Russell King Cc: Daniel Thompson Cc: Jiri Kosina Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Ralf Baechle Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: David Miller Signed-off-by: Andrew Morton --- kernel/printk/nmi.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c index 479e0764203c..303cf0d15e57 100644 --- a/kernel/printk/nmi.c +++ b/kernel/printk/nmi.c @@ -38,6 +38,7 @@ * were handled or when IRQs are blocked. */ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default; +static int printk_nmi_irq_ready; #define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work)) @@ -84,8 +85,11 @@ again: goto again; /* Get flushed in a more safe context. */ - if (add) + if (add && printk_nmi_irq_ready) { + /* Make sure that IRQ work is really initialized. */ + smp_rmb(); irq_work_queue(&s->work); + } return add; } @@ -195,6 +199,13 @@ void __init printk_nmi_init(void) init_irq_work(&s->work, __printk_nmi_flush); } + + /* Make sure that IRQ works are initialized before enabling. */ + smp_wmb(); + printk_nmi_irq_ready = 1; + + /* Flush pending messages that did not have scheduled IRQ works. */ + printk_nmi_flush(); } void printk_nmi_enter(void) -- 1.8.5.6